Chemical and physical studies of type 3 chondrites—VI: Siderophile elements in ordinary chondrites

Sears, D. W. G.; Weeks, Karen S.

doi:10.1016/0016-7037(86)90229-2

Cited by 25 publications

(22 citation statements)

References 77 publications

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“…Except for Y 74191, no prior results exist for comparison with our data in Table 3. The Sears and Weeks (1986) data for Au, Co and Ga agree with ours to within 25%, 5% and 18%, respectively. These relatively small siderophilic element differences do not affect our discussion.…”

Section: Resultssupporting

confidence: 89%

Trace elements in primitive meteorites—VII Antarctic unequilibrated ordinary chondrites

Wang

Lipschutz

2007

Geochimica et Cosmochimica Acta

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Section: Resultssupporting

confidence: 89%

Trace elements in primitive meteorites—VII Antarctic unequilibrated ordinary chondrites

Wang

Lipschutz

2007

Geochimica et Cosmochimica Acta

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“…Measurements by Dodd (1976) and Sears and Weeks (1986) suggested that the abundance of total iron in ordinary chondrites increases with petrologic type, and these authors inferred that this trend reflected increases in metallic iron. However, analyses of metallic iron in ordinary chondrites by Jarosewich (1990) show the opposite trend.…”

Section: Introductionmentioning

confidence: 99%

“…Mineralogic variations among chondrites of different metamorphic grade (petrologic type) have been previously attributed to either oxidation (McSween and Labotka, 1993) or reduction (Dodd, 1976;Brett and Sato, 1984;Sears and Weeks, 1986) reactions during metamorphism. Verification of changes in oxidation state has important implications for understanding metamorphic conditions and fluid-rock interactions in chondritic asteroids otherwise thought to have been dry.…”

Section: Introductionmentioning

confidence: 99%

A critical evaluation of oxidation versus reduction during metamorphism of L and LL group chondrites, and implications for asteroid spectroscopy

Gastineau-Lyons

McSween

Gaffey

2002

Meteorit & Planetary Scien

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Abstract-Modal mineralogies of individual, equilibrated (petrologic type 4-6) Land LL chondrites have been measured using an electron microprobe mapping technique, and the chemical compositions of coexisting silicate minerals have been analyzed. Progressive changes in the relative abundances and in the molar Fe/Mn and Fe/Mg ratios of olivine, low-Ca pyroxene, and diopside occur with increasing metamorphic grade. Variations in olivine/low-Ca pyroxene ratios (Ol/Px) and in metal abundances and compositions with petrologic type support the hypothesis that oxidation of metallic iron accompanied thermal metamorphism in ordinary chondrites. Modal Ol/Px ratios are systematically lower than normative Ol/Px ratios for the same meteorites, suggesting that the commonly used C.I.P.W. norm calculation procedure may not adequately estimate silicate mineral abundances in reduced chondrites. Ol/Px ratios calculated from visible and near-infrared (VISNIR) reflectance spectra of the same meteorites are not in agreement with other Ol/Px determinations, possibly because of spectral complexities arising from other minerals in chondrites. Characteristic features in VISNIR spectra are sensitive to the proportions and compositions ofolivine and pyroxenes, the minerals most affected by oxidative metamorphism. This work may allow spectral calibration for the determination ofmineralogy and petrologic type, and thus may be useful for spectroscopic studies of asteroids.

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“…Fe-Ni metal was analyzed at 100 spots in 19 grains ( Table 2). The results of 13 microprobe analyses in seven pentlandite grains are also given in The abundance of Au is marginally lower in Machinga as compared to average L6 chondrite abundances (Keays et al, 1971;Sears and Weeks, 1986), which may be indicative of a minimal loss of Au during shock heating. Some volatile element contents (such as Cs, Sb, As) are lower in Machinga than in average L6 chondrites, but others (such as the halogens, or Ga) have normal abundances.…”

Section: Mineral Chemistrymentioning

confidence: 99%

New mineralogical and chemical data on the Machinga (L6) chondrite, Malawi

et al. 1990

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Abstract-The Machinga, southern Malawi, Africa, L6 chondrite (observed fall, 22 January 1981) contains accessory phases of metal, troilite, chromite, and native Cu (which is associated with limonite and found in zones of aqueous alteration). Rare accessory phases are apatite and pentlandite, which are uncommon in L6 chondrites. Major mineral constituents (olivine, orthopyroxene, and plagioclase) indicate shock effects at a level of about 15-20 GPa shock pressure. The meteorite is thus classified to be of L6d type. Melt pockets of widely variable composition are abundant.

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Chemical and physical studies of type 3 chondrites—VI: Siderophile elements in ordinary chondrites

Cited by 25 publications

References 77 publications

Trace elements in primitive meteorites—VII Antarctic unequilibrated ordinary chondrites

Trace elements in primitive meteorites—VII Antarctic unequilibrated ordinary chondrites

A critical evaluation of oxidation versus reduction during metamorphism of L and LL group chondrites, and implications for asteroid spectroscopy

New mineralogical and chemical data on the Machinga (L6) chondrite, Malawi

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